Apparatus and method of coating elongated webs with light-sensitive material



May 7, 1957 Filed April 15, 1954 N. B. MEARS APPARATUS AND METHOD OF COATING ELONGATED WEBS WITH LIGHT-SENSITIVE MATERIAL United States Patent APPARATUS AND METHOD OF COATING ELON- GATED WEBS WITH LIGHT-SENSITIVE MATE- RIAL Norman E. Mears, St. Paul, Minn., assignor to Buckbee- Mears Company, St. Paul, Minn., a corporation of Minnesota Application April 15, 1954, Serial No. 423,472

9 Claims. (Cl. 117-34) This invention relates to apparatus and a methodfor forming light-sensitive coatings on elongated webs, and particularly to an improved method and apparatus for removing excess coating from the freshlycoated web during the period required for the setting of the-coating maten'al whereby to facilitate the formation of coatings of uniform thickness.

The present invention is an improvement on the machine and method for producing light-sensitive coatings on metal webs described and claimed in my application for patent Serial No. 221,904, filed April 19, 1951 and now Patent 2,710,571.

An object of my invention is to provide in coating apparatus, means for supporting an elongated web, sheet, plate or like work member to be coated with one longitudinal edge above the other longitudinal edge while-th liquid coating material is applied and allowed to set in combination with means for removing theexcessliquid coating material from the work member comprising means for submerging the lower margin of the work member in a liquid solvent for the coating material during thesetting of the coating above the submerged margin.

A further object is to provide an improved method for removing the excess liquid coating material from a freshly coated work member which comprises supporting the work with its coated surface in a vertical plane and submerging the lower margin of the work in a pool or stream of liquid solvent while allowing the coating material to set on the surface above the submergedmargin.

Other objects will appear and be more fully pointed out in the following specification and claims.

Referring to the accompanying drawing which illustrates an embodiment of my invention, by way of example and not for the purpose of limitation:

Figure 1 is a diagrammatic side elevational view showing my improved apparatus as embodied in a machine for producing light-sensitive coatings on elongated webs;

Fig. 2 is a plan view partially in section showing, my improved trough for guiding and treating the webin its passage from the coating means toward the drying means of the machine, and

Fig. 3 is a vertical sectional view taken on the line 3-3 of Fig. 1.

As shown in the diagrammatic illustration of the machine (Fig. 1), a flexible metal web, indicated generally by the numeral 4, constituting the work member to be coated, may be fed into the machine from a roll 5 upon which a supply of the web is wound. and supported with one longitudinal edge above the other. The web 4 may be extended in a substantially vertical plane from the roll 5, at one end, to a reel 6 at the opposite end and the reel 6 is, preferably, power-actuated to continuously move the web along the path indicated at a controlled, suitable speed. As more fully described in my application for patent Serial No. 221,904 and now Patent 2,710,591, the web or other work member may be subjected, as it moves along the determined path, to suitable cleaning and scouring treatment applied by apparatus indicated generally by the numeral 7. Thereupon, the web 4 is successively coated with a liquid light-sensitive material supplied through a pipe 8 .and nozzle 9 and is then guided, with its.lower edge contained in a trough 10 and itsupper edge supported by a guide 11, to a drying oven 12. The dry web is finally wound on the reel 6 after passing through the oven 12. During the movement of the freshly coated web with its lower margin guided in the trough 10, the excess coating liquid drains into this trough and the coating on the area above the lower margin sets sufliciently so that it is no longer fluid. The portion of the web extending from the coating means to the drying oven, between the trough 10 and guide 11 is preferably enclosed in a housing (not shown) to protect the freshly coated surfaces from atmospheric dust. The rate of setting of the coating may be increased by applying warm air or mild heat to the coated surfaces before they reach the drying oven.

A liquid light-sensitive material, for example, either a cold top or hot top enamel of any of the compositions commonly used in the photo-engraving art may be continuously supplied under suitably low pressure through the pipe 8 so that the liquid flows from the openings or opening 9a in the nozzle 9 to the upper margin of the web 4. Where both sides of the web 4 are to be coated, the nozzle 9 may be provided with duplicate outlet openings 9a (Fig. 3) from which the liquid is discharged upon the Web margins. The nozzle 9 is designed to avoid breaking up the emitted stream into a spray because it is desirable to cause the coating liquid to flow freely in a localized stream downward from the point of application of the stream to the web inorder to uniformly coat a surface of the web, while an excess of the coating liquidmerely falls from the lower margin of the web below the nozzle 9.. This excess liquid may be returned to the pipe 8 by suitable means.

My improved trough 10 is preferably of Vshape in cross section and is continuously supplied with a solvent for the coating material whichflows from headers 13. fastened to and extending along theside walls of the trough. Each header has a discharge slot 14 extending continuously along a side of the trough 10 from which the sol vent flows into the trough and each of the headers may be supplied with solvent-from a pipe 15 connected thereto. Water may be used as the solvent for most of thecommonly used hot top or cold top enamels.

Outlet openings 16 are formed in the bottom of the trough 10 at suitable intervals and are so related in size and number to the rate of supply of the solvent from the openings 14 as to maintain, continuously along the bottom of the trough 10, a shallow pool 17 of the solvent. This pool is a flowing stream which is continuously replaced so that-it washes away the excess coating materialrapidly from the lower margin of the web 4. Since this margin of the web is supported and guided along the bottom .of the-trough 10, it is continuously submergedin the solvent as it is moved along toward the drying oven from the coating apparatus. As further shown in Fig. 3, the discharge from the openings 16 is caught in apan 18 extending along beneath the trough 10- and may be conducted to waste through a pipe 19.

Inoperation, theweb4 with its freshly coated surfaces 40 is maintained under suitable longitudinal tension as it is moved continuously along from the roll 5 to the reel 6. In traveling along this determined path, the surface of the web is first thoroughly cleansed by the apparatus indicated diagrammatically at 7 and then coated with the liquid light sensitive material flowing from the nozzle 9. The coating material is then allowed to set and is dried while the web is moved through the drying oven 12, to be finally wound on the reel 6.

In passingfrom the coating apparatus to the drying oven, the lower margin of the web is guided along the trough and is continuously submerged in the pool 17 of flowing solvent for the coating material while the coating above the submerged margin sets sufiiciently to form a substantially solid coat of the required uniformity in thickness and continuity. Thus the excess coating material as it becomes viscous and tacky does not accumulate or build up along the lower portions of the web but is washed away while free flow downward from the areas above is insured by the moistening of the margin up to the moment when the coating solidifies. This continuous removal of accumulations of the coating and moistening of the web along its lower margin is an important factor in the formation of coatings of the required uniformity of thickness and continuity.

By this invention I not only improve the quality of the coating, but I also efiect important economies by making it unnecessary to wipe oil the excess of coating by mechanical means and I materially reduce the cost of removing gummy deposits of the coating from the apparatus and maintaining it in continuous working order.

I claim:

1. The method of coating an elongated web which comprises, continuously moving said web endwise along a determined path with one longitudinal edge above the other longitudinal edge, coating a surface of the web while the web is in motion along said path by applying merging the lower margin of the web in a flowing stream of liquid solvent for the coating while allowing the coating above the submerged margin to set.

6. In apparatus having means for moving an elongated web along a predetermined path with one longitudinal edge above the other, coating means for applying a coat of liquid light sensitive material to a surface of the Web while in continuous movement along said path and means for drying said coat spaced along said path, the improvements which comprise, a trough disposed to receive the lower margin of the freshly coated web in its movement along said path from said coating means toward said drying means and means for maintaining in said trough a shallow pool of liquid solvent for the coating material whereby the lower margin of the web is submerged in said pool and excess coating material is removed during the setting of the coating above the submerged margin of the web.

. i e 7. In apparatus having means for moving an elongated web along a determined path with one longitudinal edge above'the other, coating means for applying a coating of, liquid light sensitive material to a surface of the web :while in' continuous movement along said path and means for drying said coat spaced along said path, the improvethereto a liquid light sensitive enamel and removing the excess enamel by submerging the lower margin of the web in a liquid solvent for the enamel while allowing the enamel coat above the submerged margin to set on said surface of the web.

2. The method of coating an elongated web whic comprises, continuously moving said web endwise along a determined path with one longitudinal edge above'the other longitudinal edge, delivering a liquid light sensitive material to the upper margin of the Web and coating a surface of the web by flowing said liquid downward over said surface while the web is in continuous motion along said path and removing the excess coating material by submerging the lower margin of the web in a liquid solvent for the coating material while allowing areas of the coating above the submerged margin to set on said surface of the web.

3. The method of coating an elongated web which comprises, continuously moving said web endwise along a determined path with one longitudinal edge above the other longitudinal edge, coating with a liquid light sensitive enamel a surface of the Web while the web is in motion along said path and submerging the lower margin of the web in a flowing stream of liquid solvent for the coating material, while allowing the coating above the submerged margin to set on said surface of the web.

4. In the coating of an elongated web with light sensitive material, the method of removing excess liquid coating from an elongated web which comprises, supporting the freshly coated web with. one longitudinal edge above the other longitudinal edge and submerging the lower margin of the web in a liquid solvent for the coating while allowing the coating above the submerged margin to set.

5. In the coating of an elongated Web with light sensitive material, the method of removing excess liquid coating from an elongated freshly coated web which comprises, supporting the freshly coated web with one 1ongitudinal edge above the other longitudinal edge and subments which comprise, a trough disposed to guide the lower edge of the freshly coated web along said path from said coating means toward said drying means and means 'for maintaining in said trough a flowing stream of liquid solvent for the coating material whereby the lower margin of the web is submerged in said stream during the setting 'of the coating above the submerged margin of the web.

1 8. In apparatus having means for moving an elongated web along a determined path with one longitudinal edge 7 above the other, coating means disposed to deliver a stream bfliquid light sensitive material to the upper margins of the web and to cause said liquid to flow downward over both' sides of the web while in continuous movement along said path and means for drying said coat 'spacedalong said path from said coating means, the improvements which comprise, a V-shaped trough disposed to guide the lower edge of the freshly coated web along said path from said coating means toward said drying means, and'means for maintaining in said trough "a fiowingstreain of liquid solvent for the coating material whereby the lower margin of the web is submerged 'in said stream during the setting of the coating above the submerged margin of the web.

'9. In apparatus of the class described-means for coating a work member with liquid light-sensitive material, means for supporting the freshly coated work member with one longitudinal edge above the other, longitudinal edge, and means for removing excess coating material *from the lower margin of said web comprising a trough I '-disposed to contain the lower margin of the freshly coated web during the setting of the coating material above said margin and means for maintaining in said trough a supply of liquid solvent for the coating material suiti- -'cient to' submerge said margin in the solvent during the setting of the coating material above.

'Rcfer e nces Cited in the file of this patent K UNITED STATES PATENTS 1,313,655 Weinheim Aug. 19, 1919 2,235,978 Braucher -Q. Mar. 25, 1941 1 2,279,686 if Kerlin Apr. 14, 1942 

1. THE METHOD OF COATING AN ELONGATED WEB WHICH COMPRISES, CONTINUOUSLY MOVING SAID WEB ENDWISE ALONG A DETERMINED PATH WITH ONE LONGITUDINAL EDGE ABOVE THE OTHER LONGITUDINAL EDGE, COATING A SURFACE OF THE WEB WHILE THE WEB IS IN MOTION ALONG SAID PATH BY APPLYING THERETO A LIQUID LIGHT SENSITIVE ENAMEL AND REMOVING THE EXCESS ENAMELS BY SUBMERGING THE LOWER MARGIN OF THE WEB IN A LIQUID SOLVENT FOR THE ENAMEL WHILE ALLOWING THE ENAMEL COAT ABOVE THE SUBMERGED MARGIN TO SET ON SAID SURFACE OF THE WEB. 